Method for direct percussive ignition of stable explosives, and apparatus therefor



R. c. KVAVLE 3,283,657 METHOD FOR DIRECT PERCUSSIVE IGNITION OF STABLE Nov. 8, 1966 EXPLOSIVES, AND APPARATUS THEREFOR 2 Sheets-Sheet 1 Filed May 29, 1964 N m Q/ 1% R a, Q

Inventor Robert C Kz/az/Ze By his Attornr y Nov. 8, 1366 R. c. KVAVLE 3,283,657

METHOD FOR DIRECT PERCUSSIVE IGNITION OF STABLE EXPLOSIVES, AND APPARATUS THEREFOR Filed May 29, 1964 2 Sheets-Sheet 2 &

INVENTOR ROBERT C. KVAVLE ATTORNEY United States Patent 3,283,657 METHOD FOR DIRECT PERCUSSIVE IGNITION 0F g'lABLE EXPLOSIVES, AND APPARATUS THERE- R Robert C. Kvavle, Hillsboro, Oreg., assignor, by mesne assignments, to United Shoe Machinery Corporation, Boston, Mass., a corporation of New Jersey Filed May 29, 1964, Ser. No. 371,242 14 Claims. (Cl. 891) This application is a continuation-in-part of the application of Robert C. Kvavle for Method for Direct Percussive Ignition of Stable Explosives, filed March 30, 1964, Serial No. 355,587, now abandoned.

The present invention relates to the defiagration of stable or low explosives, and more particularly to the deflagration of stable or low explosives by striking or rapidly compressing -a charge of low explosive directly in a confining, substantially closed chamber, the deflagration operating an explosively actuated tool or device to'impart energy, such as kinetic energy, to an element in the tool or device by the gases evolving from the deflagration'of the charge.

As is well known, the cartridge used in firearms, explosively-actuated tools, etc., in addition to containing the gunpowder or other explosive charge, necessarily also is provided with an easily detonated primer, which, when acted upon by percussive means, produces ignition of the explosive charge in the cartridge. This primer itself is highly unstable and sensitive to physical shock and consequently adds certain hazards to the manufacture, shipping and handling of such commonly used cartridges.

The above mentioned customary cartridge includes some sort of casing or housing, of brass or the like, for the primer and the main explosive charge, and it has been necessary to extract or withdraw the casing from the explosive tool after the cartridge has been fired because the casing is not combustible.

Other known methods for igniting low explosives utilize electricity, or the contacting of the explosive with a burning or heated element or material.

An object of the present invention is to provide a method of deflagrating a low explosive in an explosively actuated tool or the like without resort to a primer, electric charge, or heated element or material.

Another object of the present invention is the provision of a method for deflagrating an explosive in an explosively actuated tool or the like which does not require the introduction of a noncombustible cartride easing into the firing apparatus.

Yet another object of the present invention is to provide a method of deflagrating a low explosive in an explosive tool or the like through the use of a relatively small amount of mechanical or manual energy.

Another object of the present invention is the provision of a method for deflagrating a complete charge of a low explosive by percussion, or rapid compression to operate a tool or device.

Another object of the present invention is to provide a method for operating an-explosively actuated tool or device in which a relatively large amount of stable explosive is deflagrated through rapid compression or impacting of a portion of the charge.

Yet another object of the present invention is the provision of a method for causing explosive defiagration of a low explosive wherein a portion of the entire charge is deflagrated by rapid crushing of impaction frictionally generating heat, with subsequent defiagration of the remainder of the charge from the explosive products evolved by the initial deflagration.

A further object of the present invention is to provide "ice simple apparatus for utilizing the method(s) of the present invention.

Other objects and many of the attendant advantages of the present invention will be understood from the following specification and drawings, wherein:

FIGURE 1 is a sectional side elevation of a simplified device capable of carrying out the method of the invention showing the device loaded with a gunpowder pellet and ready for firing;

FIGURE 2 is a transverse section on line 2-2 of FIG- URE 1; 1

FIGURE 3 is a sectional side elevation of a device similar in most respects to the device of FIGURE 1 but embodying a modification;

FIGURE 4 is an elevation of a gunpowder pellet suitable for use in either the device of FIGURE 1 or FIG- URE 3;

FIGURE 5 is a longitudinal section of another embodiment of an explosive tool; and

FIGURE 6 is an end view of the embodiment shown in FIGURE 5.

In accordance with the present invention, a charge of relatively stable low explosive, such as ordinary gunpowder, is completely deflagrated by direct action on the charge, thus eliminating any requirement for primers of any sort, whether explosive, electrical, heat, etc. This is accomplished by rapidly compressing part or all of the charge While it is in a substantially closed confining chamber. The term rapidly compressing as used herein includes a striking of the charge by one or more surfaces while the charge is held on or resting against another surface or surfaces, or the carrying of a charge by one surface as it moves toward another surface and causes the charge to strike the other surface with the resultant initiation of combustion of one. or several elemental par ticles of the explosive charge. By a confining chamber is meant a chamber which is so small, relative to the size of the charge, that upon the combustion of the above mentioned one or several elemental charge particles, there will result a confinement of the evolved gases so that there is obtained the defiagration or combustion of the remainder of the charge, this progressing in a generally accelerating, cumulative or exponential-like manner; by confining is means the act of placing or introducing a charge into a chamber which is or becomes a confining chamber. By substantially closed chamber is meant a chamber which is sufficiently sealed or sutficiently leakproof that the build-up of the explosion may proceed, without dissipation of the gas pressure to such an extent that the above-mentioned progressive accelerating deflagration cannot occur.

The gases evolving from the defiagration are used to impart kinetic energy to a movable element, which may be a piston-like element in an explosive tool, a projectile as in an explosive tool or other device, etc,; the energy of these gases may be otherwise used to perform work as by imparting other type(s) of energy to an element or material.

Referring first to FIGURES 1 and 2, an end housing block 10 has a tubular barrel 11 secured thereto by a, threaded connection 12. The housing block 10 has a cylindrical recess 13 which may be of the same diameter as the internal diameter of the tubular barrel 11 and the recess 13 and barrel 11 are co-axial so that when the tubular barrel is secured to the housing block the recess 13 and barrel 11 combine to form in effect a barrel with the breech end in the block 10. An end collar 14 is drical wall of the sleeve is preferably provided with a knurled surface. A coil spring 16 is carried on the barrel 11 and is held under compression at all times between the end collar 14 and the sleeve 15.

A spring-controlled sear lever 17 is pivotally mounted on a pin 18 in a notch 19 provided in the outer wall of the housing block 10. The outer end of the sear lever 17 is formed with a shoulder 17' for engaging the flange 15' of the firing sleeve. A spring 20 engages the opposite end of the sear lever 17, the bottom end of this spring 20 being held in a socket recess 21 leading radially inwardly from the notch 19. This end of the sear lever is formed with a radially outwardly extending finger grip portion or trigger 22.

As apparent from FIGURE 1, when the firing sleeve 15 is in the cocked position shown, then downward or inward pressure on the trigger 22 against the force of spring 20 Will release the firing sleeve 15 and allow it to be driven to the right (as viewed in this figure) under the force of spring 16. Then, upon manual movement of the sleeve 15 back to the left, the sear lever 17 will again engage the sleeve 15 and hold the sleeve in cocked position.

The lower portion of the housing block 10 is formed with a cylindrical chamber 23, preferably smaller in diameter than the recess 13 and barrel but preferably with its axis parallel to that of the recess 13 and the barrel. The end of this chamber toward the muzzle end of the device is connected to a co-axial cylindrical passageway 24 of smaller diameter which leads to the end of the housing block 10. The other end of the'chamber 23 is closed by a plug 25.

A short channel 26 connects the chamber 23 with the recess 13 or breech end of the barrel, this channel 26 being located substantially as illustrated in FIGURE 1 and thus being spaced a short distance in from the end of the plug 25 and substantially at the breech end of the barrel.

Another open channel 27 connects the chamber 23 with the outside through the outer housing wall. This open channel 27 is located further forward (thus further to the left as viewed in FIGURE 1) than the channel 26, the relative locations of the two channels 26 and 27 being substantially as shown in FIGURE 1.

A firing pin 28 is slidably mounted in chamber 23, the firing pin having a diameter substantially equal to that of the chamber 23 so that the cylindrical surface of the firing pin fits the cylindrical wall of the chamber with a close tolerance. The firing pin 28 has an axially aligned reduced diameter extension 29 which extends out through the passageway 24 and has a sliding fitwith the wall of the passageway. The junction between the main body of the firing pin 28 and its reduced extension 29 forms an annular shoulder 29'. Similarly the junction between the chamber 23 and the passageway 24 forms an annular shoulder 30 in the surrounding wall.

As shown in FIGURE 1, the axial length of the firing pin 28 is considerably less than the axial length of the chamber 23, and a coil spring 31 is mounted in the annular space between the shoulders 29' and 30. The coil spring 31 is held under compression at all times, but is not a strong spring, its purpose being merely to maintain the firing pin urged as far as possible to the right (as viewed in FIGURE 1). The outer end of the firing pin extension 29 is provided with a suitable handle 32 so as to enable the firing pin to be pulled to the left against the spring 31 for the purpose of loading the chamber 23 preparatory to firing the device, as presently explained.

A pellet 33 (see also FIGURE 4) of ordinary gunpowder (or similar stable explosive) is used in carrying out the method of the present invention, and is, significantly, not placed within any non-combustible casing nor is it associated with any primer. The pellet 33 may, for example be made up either of gunpowder exclusively, pressed together so that it coheres, or it may be made of gunpowder with a binder material which will completely 4- gasify without residue or deposit during or after the explosive process. The pellet 33 must be of course of smaller diameter than the chamber 23 and piston 28.

The loading of the device is accomplished as follows: The firing sleeve 15 is pulled (to the left) into the cocked position of FIGURE 1. Next the piston 28 is moved to the left by manual pull on the handle 32 until the channel 27 is uncovered, allowing access to the chamber 23. With the firing pin manually held in this position a pellet 33 is inserted into the chamber 23 through the open channel 27. The firing pin 28 is then allowed to move to the right until the movement of the firing pin is stopped by the engagement of the pellet 33 with the plug 25 or end of the firing chamber. Under this condition there will be a small amount of air together with the pellet 33 in the temporarily sealed space between the plug 25 or end of the firing chamber and the opposed end of the firing pin 28, the channel 26 also being closed off by the firing pin. The device is now ready for firing.

When the pressing of the trigger 22 releases the firing sleeve 15 the latter, under the force of the spring 16, strikes the outer end of the firing pin extension 29. The kinetic energy from the impact results in the firing pin impacting and rapidly compression the gunpowder pellet or charge whilesimultaneously compressing the entrapped air. While some air space is shown in FIGURE 1 be tween the charge pellet 33 and the boundary walls defin ing the substantially closed, confining firing chamber, it is not necessarythat such air space externally of the charge pellet 33 exist. This is because the charge pellet 33 is itself somewhat granular in structure, and thereby has air between the individual particles forming the pellet itself. The combination of the compression of the powder granules with the compression of the entrapped air within the pellet and in the confining, substantially closed chamber results in the explosive deflagration of the entire pellet charge. It is believed that air is compressed adiabatically and heats, and/or at least one or a relatively few of the powder grains are compressed, viscously flow and heat, and/or the friction of the powder grains rubbing against other powder grains and against the surface of the confining Walls generates heat, so that one or several grains are, therefore, ignited, thus evolving hot and rapidly expanding gases. Due to the fact that the chamber is substantially'closed and is relatively small, thereby confining these hot gases, they do not escape, but instead serve to ignite other powder granules. This process continues at an accelerating rate so that there results the explosive deflagration of the entire pellet charge. The hot gases from the deflagration then blow out through the channel 26 into the breech end of the barrel as the firing pin, being thrust back (to the left), uncovers the channel 26. The further thrust on the firing pin, and

' therewith on the firing sleeve 15, as the hot gases blow out through the channel 26, is absorbed mainly by the firing sleeve spring 16.

- It is known that gunpowder burns more rapidly and efiioiently at an elevated pressure. On the other hand, it has been observed, that, while a few individual particles of gunpowder charge can be ignited in open air by strong hammer-like blows, the heat energy from these initially burned particles is dissipated too rapidly to ignite and produce complete combustion of all the gunpowder since,

' as is known, gunpowder does not burn efliciently in open air. I In accordance with the present invention, the explosive defiagration of the gunpowder (or other low explosive solid material) is brought about by having the gunpowder rapidly compressed in a surrounding environment enabling rapid build-up of sufiiciently high pressure, or being of sufiiciently high pressure, to cause burning of the entire charge.

FIGURE 3 illustrates another embodiment of the method of the present invention wherein only a portion of the powder charge is subjected to rapid compression.

Thus, as is shown in FIGURE 3, the plug 25', which forms the end of the combustion chamber 23, is formed with an axial cavity 34 of small diameter. The piston 28' has a protrusion 35 in axial alignment with and of substantially the same diameter as the cavity 34 so that the protrusion 35 fits the cavity 34 with a Close tolerance.

When the firing pin 28' receives the impact from the released firing sleeve 15 the kinetic energy of the firing pin is utilized to act through impact of the protrusion 35 upon only a small portion of the pellet 33, forcing that portion into the cavity 34, which is an ignition cavity. The portion of the charge pellet 33 which has been forced into ignition cavity 34 is rapidly compressed therein, and, as will be understood, the said portion of charge pellet 33 is subjected to the rapid compression and crushing and hence frictionally generated heat in a confining chamber which is substantially closed. As described in connection with FIGURE 1, one or several of the powder granules will ignite and the ignition process will then proceed within the ignition cavity 34. The evolved gases will act on the protrusion 35 and force it and the piston 28' to the left, so that protrusion 35 is forced out of the ignition cavity 34. At this instant, the gases in ignition chamber 34 rapidly expand into chamber 23 and cause the ignition of the remaining portion of the pellet 33, and since it is, at this instant, in a confining, substantially closed chamber, the piston 28 and/ or the charge 33 not having yet efiectively opened the passageway 26, defiagration of this remaining portion of the charge pellet 33 occurs. Thereafter, the action proceeds as in FIGURE 1, piston 28' being forced away from the anvil means with the gases entering the barrel 13 through the now uncovered channel 26.

With the embodiment of the invention illustrated in FIGURE 3, a relatively lesser amount of energy is required for the operation of the firing pin, in comparison with the operation of the method as illustrated in FIG- URE 1. This result is obtained since the percussive impact or compression and crushing is delivered on a relatively small amount of the explosive charge by the relatively small protrusion of the firing pin.

While the ignition cavity has been disclosed in the plug, with the firing pin carrying the protrusion, it will be apparent that the firing pin could be provided With the ignition cavity, with the plug having the protrusion.

A practical embodiment of the invention having an ignition chamber about two-tenths of an inch in diameter and one-eighth inch deep is efiective to drive a pin into a steel plate, using approximately four grains of ordinary gunpowder.

Referring now to FIGURE 5, the-re is shown a gunshaped body 50 having a passage 51 leading to a chamber 52. A piston 53 having a piston rod 54 is urged against one wall of chamber 52 by a spring 56. An abutment 57 is provided in chamber 52 to limit the travel of piston 53. A relatively small firing chamber 58 is provided having a spring urged anvil 59 the-rein, chamber 58 communicating with piston chamber 52 through a passage 61 which is spaced somewhat below the upper edge of anvil 59 when that piston is in its upper position, as shown in FIGURE 5. Above the anvil 59 is a chamber 62 communicating with a passage 63.

A striker 65, in the form of a lever, has a head 66 at the upper end and is mounted on a transverse pivot shaft 67. Fixed to the striker 65 is a cocking lever 68, which includes a handle 6%. The lower end 71 of the striker 65 is urged in a counterclockwise direction by a relative-1y strong spring 72 anchored at 68. A trigger 73 is urged in a clockwise direction by a weak spring 74 to engage with an abutment 76. Trigger 73 is provided with an engaging part 77 which serves to hold the lever 65 in a cocked position by engagement with the lower end 71 thereof. p p

A dispenser 80 in the form of a disc having a plurality of chambers 81 is rotatably mounted by a pin 82 in body 6 50. An ejector pin 83 is slidable in body 50, and is urged inwardly by spring 84.

In operation, a member to be fired from the device 50 may be placed in the passage 51 and engaged with the end of the piston rod 54. The cocking lever 68 is rotated in a clockwise manner into the position shown in FIGURE 5, the lower end 71 of lever 65 striking the part 77 of trigger 73 and causing the trigger 73 to rotate against the urging of spring 74, to thereby permit lower end 71 to pass across the part 77; after it has passed, trigger 73 will be rotated into the position shown in FIGURE 5 where it will serve to hold the lever 65 in the position shown in dotted lines. Dispenser is then rotated so as to bring a chamber 81 opposite ejector pin 83, spring 84 forcing ejector pin 83 to the left as seen in FIGURE 6 to thereby eject a powder pellet 33 from the chamber 81 into chamber 62, so that it will come to rest on the anvil 59.

Trigger 73 is actuated in the usual manner to thereby release the striker 65; this enables the spring 72 to cause striker 60 to rotate, so that head 66 passes through passage 63 and chamber 62 and then first rapidly compresses the pellet charge 33 against the anvil 59 in chamber 62, and thereafter moves the pellet 33 and anvil 59 into confining chamber 58, which is sufliciently small that it acts as a confining chamber. The pellet charge will thereby be ignited in the above-described manner, and the gases evolved from the ignition will pass through passage 61 and cause the piston 53 to move to the left against the urging of the light spring 56, until it engages with the abutments 57, thereby causing a projectile-like element to be driven from the passage 51.

In FIGURES 5 and 6, therefore, rapid compression of the powder charge begins, after which it is confined in the confining chamber. As will be understood, the construction of striker head 66 and anvil 59 may be in accordance with the construction shown in FIGURE 3, in which there are an ignition chamber and a combustion chamber.

It will be also understood that the explosive charge need not be pelletized since the invention may be practiced with the explosive in powder form. I

It will be obvious to those skilled in the art that various changes may be made Without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

What is claimed is:

1. A method of operating an explosively actuated device comprising confining asolid caseless charge consisting of relatively stable low explosive and entrapped air in a substantially closed chamber, initially venting said chamber 50 as to release pressure of the air about the charge in said chamber, rapidly engaging and crushing by impact at least part of said charge after the chamber is substantially closed to thereby explosively deflagrate at least a portion of said charge with consequent evolution of gases, and causing the gases evolved from continued defiagration throughout said charge to impart energy to an element.

2. The method of operating a fastener driving tool comprising confining a charge of relatively stable low explosive in a substantially closed chamber of the tool, rapidly engaging byimpact and then compressing at least part of said charge to thereby explosively deflagrate at least a portion thereof with consequent evolution of gases, placing a second charge of relatively stable low explosive in a second substantially closed confining chamber of the tool, admitting at least part of the evolved gases from said first mentioned chamber to said second chamber to thereby cause explosive deflagration of said second charge and evolution of gases therefrom, and directing substantially all of the gases evolved to drive a fastener out of the tool.

3. A method of operating an explosively actuated device comprising introducing into a confining ignition chamber a portion consisting of less than half of a charge of relatively stable low explosive While retaining the remainder of said charge in a substantially closed confining firing chamber, substantially closing said ignition chamber, rapidly engaging by mechanical impact and then compressing said portion of said charge in said ignition chamber to deflagrate at least part of said portion of said charge passing gases evolved from the deflagration of said portion of said charge to said firing chamber to thereby deflagrate at least part of the remainder of said charge and increase the pressure in said firing chambenand causing said gas to impart kinetic energy to a movable element to be driven by the device.

4. A method of operating an explosivelyactuated tool comprising introducing into a confining ignition chamber in said tool a portion of a charge of relatively stable low explosive While retaining the remainder of said charge in a substantially closed confining firing chamber in said tool, substantially closing said ignition chamber, rapidly compressing by mechanical impact said portion of said charge between surfaces in said ignition chamber, whereby to deflagrate said portion of charge, passing gases evolved from the defiagration of said portion of said charge to said firing chamber to thereby defiagrate the remainder of said charge and increase the pressure in said firing chamber, and causing the pressurized gas to impart kinetic energy to a movable element to be driven by said tool.

5. The improvedmethod ofobtaining explosive deflagration of a caseless charge of gunpowder or other solid stable explosive of crushable material directly by impact which comprises preparing the charge in pellet form, providing an ignition chamber, initially venting said chamber so as to release pressure of the air about the charge insaid chamber, providing a firing pin for said chamber so arranged that said firing pin will compress the air in said chamber immediately about the charge and in the charge when kinetic energy is imparted to said firing pin and the chamber is substantially closed, arranging said pellet in said chamber with said pellet held between the end wall of said chamber and said firing pin, and causing kinetic energy to be imparted to said firing pin for producing direct mechanical impact on said pellet, whereby the air in and about said pellet in said chamber will be raised to an elevated pressure by said firing pin simultaneously with the delivery of the direct impact upon and crushing of said pellet and thereby aid in producing the explosive deflagration of said pellet.

6. In an explosively actuated device, a first relatively large cylindrical chamber having a closeable exhaust port, a second relatively small cylindrical chamber coaxial therewith and adjacent thereto, a striker of substantially the same diameter as said first chamber movable axially therein toward and from said second chamber to close and open said exhaust port and having a protrusion thereon of substantially the same diameter as said second chamber and coaxial therewith, and manually operable means for elfecting impacting movement of said striker element toward said second chamber and to close said port whereby said protrusion may cooperate with said second chamber and frictionally crush a non-liquid, low explosive charge therein to initiate defiagration and upon resultant movement of the striker element away from the second chamber the port is uncovered to direct gases evolving from the deflagration.

7. An explosively actuated device comprising a sub stantially closed chamber, an anvil mounted for movement to a position within said chamber, striker means for impacting and crushing at least a portion ofa solid low explosive charge on said anvil and' for driving said anvil into said chamber, means for venting the chamber immediately prior to the striker means impacting the charge, the striker means substantially closing the chamber upon impacting the charge, means for receiving a movable element adapted to be driven by gases evolved in said chamber, and means for conducting gases from said chamber to said receiving means.

8. A method of operating an explosively actuated device comprising introducing into a confining ignition chamber a portion of a porous charge of relatively stable low explosive while retaining the remainder of said charge in a substantially closed confining firing chamber, substantially closing said ignition chamber, rapidly engaging, compressing and crushing said portionot said charge in said substantially closed ignition chamber, whereby to defiagrate at least part of said portion of said charge, and passing gases evolved from the deflagration of said portion of said charge to said firing chamber to thereby defiagrate under pressure at least part of the remainder of said charge and increase the pressure in said firing chamber.

9. In an explosively actuated tool for driving an element such as a ram or stud, a barrel having a closed end for receiving and guiding the element to be driven, means including an anvil for confining a solid caseless charge of low explosive, striker means mounted for movement toward and from cooperative engagement with said anvil, means for causing the striker means to directly engage and thereafter rapidly. compress at least a portion of said charge against the anvil, and a passageway extending between said charge. confining means and the closed end of said barrel, the arrangement being such that at least one of the striker means and the charge maintains the passageway closed as the striker means directly engagesand deflagratesat leastsaid portion of the charge,

and thereafter opens said passageway to the closed end of the barrel, the defiagration continuing throughout the charge in the confining means under pressure of the gases evolved therein, and the element being driven by their discharge through said passageway into said barrel end.

10, A tool as set forth in claim 9 and further characterized in that said means causing the striker means to engage and compress at least a portion of the charge includes a spring, means for storing energy in the spring, and means for transmitting the stored energy of said spring to said striker means, said spring being arranged yieldingly to resist movement of the striker means when the latter is opening said passageway.

11. A tool as set forth in claim 9 characterized further in that said striker means includes a firing pin, and said charge confining means includes an ignition cavity corresponding in shape to and cooperative with the firing pin, one of the firing pin and the ignition cavity having a small protrusion for high pressure impact against a small portion of the charge backed by the other of the firing pin and the ignition cavity.

12. In an explosively actuated, hand operated tool for driving fastener elements such as drive pins or the like, a first relatively large chamber adapted to substantially confine a charge of low explosive, a second relatively small chamber communicating therewith, striker means for directly engaging and then crushing a charge in said second chamber to initiate deflagration accelerative into said first large chamber, and means including a vent in said large chamber for directing gases evolving from the deflagration to propel a fastener element, the last-mentioned means being rendered effective by combustion of the charge in the first chamber upon substantial completion of deflagration therein.

13. In an explosively actuated device, a first relatively large cylindrical chamber having an exhaust port, a second relatively small cylindrical chamber coaxial with the first chamber and adjacent thereto, a striker of substantially the same diameter as said first chamber movable axially therein and having a protrusion thereon of substantially the same diameter as said second chamber and coaxial therewith, and means for moving said striker toward said second chamber to cause said protrusion to 9 engage a low explosive charge and then compress a portion thereof in said second chamber to initiate defiagration, subsequent movement of the striker away from the second chamber uncovering said port to discharge pressurized gases evolving from the deflagration.

14. In a tool for explosively driving a fastener, a chamber formed to receive a charge of low explosive and provided with an exhaust port, firing mechanism operable in said chamber for substantially confining the charge therein and including a charge impacting protrusion, said chamber having an ignition cavity less than one-half the volume of the chamber and adapted to receive that portion of the charge to be engaged by the impacting protrusion and thus be ignited during operation of the firing mechanism in one direction, whereby defiagration under pressure of the gas evolved in said cavity can progress into said chamber during movement of said mechanism in another direction and further generate gas under pressure to be exhausted through said port for driving the fastener.

References Cited by the Examiner lished Nov. 7, 1957. BENJAMIN A. BORCHELT, Primary Examiner.

2O SAMUEL W. ENGLE, Examiner.

F. C. MATTERN, Assistant Examiner. 

1. A METHOD OF OPERATING AN EXPLOSIVELY ACTUATED DEVICE COMPRISING CONFINING A SOLID CASELESS CHARGE CONSISTING OF RELATIVELY STABLE LOW EXPLOSIVE AND ENTRAPPED AIR IN A SUBSTANTIALLY CLOSED CHAMBER, INITIALLY VENTING SAID CHAMBER SO AS TO RELEASE PRESSURE OF THE AIR ABOUT THE CHARGE IN SAID CHAMBER, RAPIDLY ENGAGING AND CRUSHING BY IMPACT AT LEAST PART OF SAID CHARGE AFTER THE CHAMBER IS SUBSTANTIALLY CLOSED TO THEREBY EXPLOSIVELY DEFLAGRATE AT LEAST A PORTION OF SAID CHARGE WITH CONSEQUENT EVOLUTION OF GASES, AND CAUSING THE GASES EVOLVED FROM CONTINUED DEFLAGRATION THROUGHOUT SAID CHARGE TO IMPART ENERGY TO AN ELEMENT. 